DSAX110 Redundant Board Problem

Hi, I have an AC450 2.3 with 3 Redundant DSAX110 boards with connection unit DSTA 001A.
The redundant board of AXR2 gave error and the primary one is working properly so I changed the redundant Board and it works well for few days then it gave error once again.
After that I removed the board and inserted it again and it works fine for less than 1 hour and it gave error again.
So do I need to change the board again or change the connection unit?

Thanks alot